I am posting an early design sketch of a 2m WSPR beacon.

Here are the key points:

  • 25 MHz HCI 0.5ppm TCXO powering the Si5351 module instead of the 26 MHz TCXO.

    If this fails, we can use a 10 MHz OCXO instead (a bit out of spec but works fine).

  • Tokmas CID10N65F GaN FET might work @ 144 MHz as the 'final'. If not, use Mitsubishi RD15HVF1-501 MOSFET as backup.

  • 2SK3475 as the driver with variable DC bias at the gate

  • The whole VCC to this amplifier will be PTT switched

  • Ideally, we would want to keep the driver stage linear but the final stage as switched (Class C/D)

    Alternate: Perhaps by DC coupling the Si5351 input to 2SK3475, we can avoid the need for DC gate bias

  • The "RFC" (bifilar coil still needed?) part will need to be figured out for VHF!

Results: To be built and tested soon!

Update: There is NO 2m "SSB / FT8 / WSPR" traffic in India it seems.

Update 2: See https://rfzero.net/documentation/third-party-solutions/pa-50-mhz-aft05ms031n/ for inspiration!